Small high current dc relay structure

ABSTRACT

A small high-current DC relay having a closed-loop magnetic core divided by two core gaps into a stationary and a movable core part; a spring armature pivotally connecting the core parts; and a coil mounted on the stationary core part. The armature is formed of a single strip of electrically conductive spring material and includes an anchorage end portion secured to the stationary core part, a supporting portion rigidly secured to the movable core part, an arcuate fulcrum portion connecting the supporting and anchorage portions and defining a sole fulcrum about which the movable core part can pivot through a first angle, a free contact portion at the other end of the armature and carrying a contact, and a flexible arm portion connecting the contact and supporting portions and defining a second angle of pivotal movement of the contact portion about the fulcrum, smaller than the first angle. Upon energization of the coil, the difference between the two pivotal angles will bow the flexible arm portion, wiping the contact across a co-operating stationary contact upon closing and opening of the contacts.

United States Patent 1191 Hayden et al.

[ June 26, 1973 1 1 SMALL HIGH CURRENT DC RELAY STRUCTURE [75] Inventors: Rodney Hayden, Stoney Creek,

Ontario; Dennis Herbert MacDonald, Hamilton, Ontario, both of Canada 731 Assignee: TRW Inc., Cleveland, Ohio 22 Filed: Aug. 2, 1970 [21] Appl. No.: 277,202

[52] US. Cl. 335/187, 335/203 [51] Int. Cl. H0lh 50/18 [581 Field of Search 335/187, 200, 202, 335/203, 189, 196

[56] References Cited UNITED STATES PATENTS 3,184,564 5/1965 Rycltman et a1 335/187 3,210,499 10/1965 Sosnoski 335/187 Primary Examiner-Har0ld Broome AttorneyCavanagh & Norman [57] ABSTRACT A small high-current DC relay having a closed-loop magnetic core divided by two core gaps into a stationary and a movable core part; a spring armature pivotally connecting the core parts; and a coil mounted on the stationary core part. The armature is formed of a single strip of electrically conductive spring material and includes an anchorage end portion secured to the stationary core part, a supporting portion rigidly secured to the movable core part, an arcuate fulcrum portion connecting the supporting and anchorage portions and defining a sole fulcrum about which the movable core part can pivot through a first angle, a free contact portion at the other end of the armature and carrying a contact, and a flexible arm portion connecting the contact and supporting portions and defining a second angle of pivotal movement of the contact portion about the fulcrum, smaller than the. first angle. Upon energization of the coil, the difference between the two pivotal angles will bow the flexible arm portion, wiping the contact across a co-operating stationary contact upon closing and opening of the contacts.

7 Claims, 6 Drawing Figures PATENIEUJUNZS um FIG2 FIG 1 SMALL HIGH CURRENT DC RELAY STRUCTURE This invention relates to a small DC relay for large currents of particular use in automobile circuitry.

There have been prior attempts to provide small size direct current relays of heavy current handling capability of the order of to 30 amperes. There are three arrangements of structure from which a selection may be made to obtain a useful organization of components. The relay in all cases will comprise a movable armature with switch contacts thereof and having a pivot point, the armature being movable about the pivot as a result of magnetic flux generated by a relay coil. The coil may be located between the pivot and contacts, or secondly the pivot may be located between the coil and the contacts, or lastly the contacts may be located between the coil and the pivot point. Prior miniature heavy current DC relays have all been of the first type with the coil between the pivot and contacts. This has led to a cost disadvantage in that the coil must be mounted within the configuration of the armature, i.e., it is partially enclosed by the armature. The arrangement is not suited to automatic production assembly especially when the coil is provided with a separate core portion which must be fastened to another core part. Attempts have also been made to utilize the springiness of an armature member in sole spring biasing function for the armature member. In such circumstances, however, an armature fulcrum has been provided by hinging a movable core part on a fixed core part providing a biasing spring function with the material of the armature member thus to limit the separation of the core parts to a single core gap. This leads to a complication in fabrication and assembly giving rise to an undue number of parts and a susceptibility to differences of adjustment of spring tension controlling the draw force for the armature.

With the above background in mind, it is therefore an object of this invention to provide a compact electromagnetic relay assembly capable of handling very high currents in proportion to its size.

It is a further object of the invention to provide such a relay characterized by a self-cleaning or wiping movement of its contacts relative to one another.

Another object of the invention is the provision of such a relay which is further characterized by an extremely long and reliable service life as compared with prior known constructions.

Still another object of the invention is the provision of such a relay which is formed in such a manner as to permit assembly of its components in a simple and rapid manner.

Additional objects and advantages will become apparent from the following detailed description of preferred embodiments of the invention, given by way of example only and read in conjunction with the accom panying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is an elevational view showing one form of relay constructed according to the present invention with parts thereof removed for clarity;

FIG. 2 is an elevational view similar to FIG. 1 showing a modified form of the invention;

FIG. 3 shows schematically pivotal movement of the relay armature of FIGS. 1 and 2;

FIG. 4 is an enlarged elevational view showing in detail relative movement between the contacts of a further modified embodiment of the invention similar to that in FIG. 1 but defining a double-throw relay;

FIG. 5 is a greatly enlarged perspective view of the relay of FIG. 1; and

FIG. 6 is an enlarged elevational view of the armature of the inventive relay shown schematically.

Referring initially to FIGS. 1 and 5, a high current relay according to the present invention is shown as comprising a base 10 of a suitable insulation material such as a phenolic resin or the like and upon which is mounted a core formed from a strip of ferrous material of uniform width and thickness. The magnetic core includes a lower, stationary core part generally designated by reference numeral 12 and rigidly secured to the base 10, which core part is generally Ushaped in configuration and includes a first or coil-supporting upstanding straight leg 14 having a free upper end 16 and a second or armaturesupporting upright leg 18 likewise having a free upper end. The magnetic core further includes an upper, movable Z-shaped core part 20 formed from said strip material defining a generally horizontal leg 22 having its free end spaced from the upper or free end 16 of the coil-supporting leg 14 by a first core gap24 and a depending leg 26 having its lower end spaced from the upper or free end of the armature-supporting leg 18 by a second core gap 28. An electromagnetic coil winding 30 mounted on spool 32, of any suitable construction, is in turn mounted upon and surrounds the coil-supporting leg 14 of the lower or stationary core part 12, and it will therefore be evident that the above-described two parts of the magnetic core define a loop-like core of generally rectangular configuration forming a closed magnetic flux circuit and divided by the core gaps 24 and 28 into the two core parts, the coil winding 30 when energized providing magnetic flux for such magnetic flux circuit.

An elongated flexible flat spring armature member of a suitable current-conducting phosphor bronze, spring steel, or similar material, generally designated by reference numeral 34, serves to pivotally and resiliently connect a movable contact to the movable contact to the movable core part 20 and to pivotally bias the end of the horizontal leg 22 thereof away from the coil supporting leg 14 of the stationary core part 12. As best seen in FIGS. 1 and 6, the spring armature member 34 is preferably formed from a single continuous strip of the spring material and includes a depending anchorage end portion 36, a support portion 38 extending generally perpendicular thereto outwardly from the magnetic core, an arcuate spring fulcrum portion 40 connecting the anchorage end and support portions, a free contact portion 42 at the outer or free end of the armature, and a free flexible arm portion 44 extending between and connecting the free contact portion 42 and the support portion 38. The depending anchorage end portion 36 is rigidly secured to the armaturesupporting leg 18 of the stationary core part 12, while the free contact portion 42 of the spring armature member carries a contact 46 defining the movable contact of the relay. While the spring armature member 34 may be secured to the armature-supporting leg 18 by conventional rivets or the like, it is preferred, in constructing the inventive relay, that the armaturesupporting leg be provided with outward protrusions or dimples, as by center-punching, which are received within corresponding openings in the anchorage end portion 36 of the armature member, and that such pro trusions or dimples then be struck to form headed portions which securely retain the armature member in place on the leg 18.

The movable core part 20 further includes an outwardly extending leg 48 generally perpendicular to the depending leg 26 thereof, thus defining a generally Z- shaped movable core member, such outwardly extending leg 48 being rigidly secured by rivets or other suitable means to the support portion 38 of the spring armature member 34 adjacent the beginning of the arcuate fulcrum portion 40 thereof. It will therefore be appreciated that, due to the resiliency of the spring armature member, the movable core part 20 will be pivotally mounted relative to the stationary core part 12 about a pivot zone defined essentially by the arcuate fulcrum portion 40 of the armature member 34, and will be biased by the the armature member upwardly away from the coil-supporting leg 14, i.e., towards the position shown in solid lines. It should further be apparent that counter-clockwise pivotal movement of the movable core part 20 towards the coil 30 resulting from energization of the latter will be transmitted to the portions 38, 42 and 44 of the spring armature member, due to the rigid connection therebetween, moving the movable core part 20 and the spring armature member 34 to their illustrated dashed-line positions.

It will be appreciated, of course, that in the event the armature member 34 consists of a ferrous material, such as spring steel, it will effectively bridge or close the second core gap 28 by virtue of the arcuate fulcrum portion 40 thereof physically connecting the stationary and movable core parts 12 and 20. In this case, the magnetic core will effectively have only a single core gap 24.

A stationary contact 50 is mounted upon the base adjacent the movable contact 46 by a suitable upstanding bracket 52, such bracket preferably being of an electrically conductive material, and in the inactivated condition of the relay this stationary contact 50 is spaced from the movable contact 46 by a contact gap 54.

Referring also to FIG. 3, it will be appreciated that the location of the upper end 16 of coil-supporting arm 14 and the spring characteristics of the spring fulcrum portion 40 of the armature will define for the free end of the movable core part a first pivotal angle of motion 0,, about the fulcrum defined by fulcrum portion 40. Further, the contact gap 54 and fulcrum portion 40 will define for the free flexible arm portion 44 and hence for the contact portion 42, a second pivotal angle of motion 6 about such fulcrum smaller than the value of angle 0,. Accordingly it will be appreciated that upon energization of the coil 30, effecting pivotal movement of the movable core part 20 and the free portion of the spring armature member 34 in the counter-clockwise direction towards their respective dashed-line positions, the movable contact 46 will engage the stationary contact 50 prior to engagement of the movable core part 20 with the upper end 16 of the stationary core part, i.e., as the movable core part 20 pivots through an angle substantially equal to 0 The movable core part will then continue to pivot through the remainder of angle 0,, until it engages or abuts against such upper end 16; however, the movable contact 46 is prevented from further outward movement by the presence of the stationary contact 50, and hence the flexible arm portion 44 of the spring armature will bow outwardly, as clearly shown in dashed lines in FIG. 1.

This outward bowing of the spring armature member shortens its effective length, and as a result the movable contact 46 will have imparted thereto an upward movement, sliding or wiping the movable contact upwardly across the stationary contact against which it abuts, as shown by the double arrow in FIG. 1. When the coil 30 is then de-energized, the above sequence will be re versed, namely, the movable core part 20 will start to pivot in the clockwise direction away from the stationary core part 12 under the influence of the spring armature; during the initial movement thereof, the movable contact 46 will remain urged against the stationary contact 50 and, as the spring armature becomes progressively less bowed, will slide or wipe downwardly against such stationary contact until the bowing compressional forces on the armature are relieved, i.e., until the movable core part 20 reaches an angle from its solid-line position substantially equal to angle-0 and the armature resumes its original or unstressed shape and effec' tive length, at which point the flexible arm portion 44 and the movable contact 46 will return to their original positions, shown in solid lines, by pivotal movement through the angle 6 about the fulcrum portion 40.

While the spring armature 34 is shown in FIG. 1 as having its free flexible arm portion 44 bent generally perpendicular to the support portion 38 so as to depend therefrom for maximum compactness of the relay construction, where space requirements are not critical the modified embodiment shown in FIG. 2 may be utilized. This modified construction is identical in structure and function with that described with reference to FIG. 1 except that the free contact portion 42 and the free flexible arm portion 44 are generally colinear with the support portion 38 and form a straight continuous extension thereof, such that the pivotal movement of the contact portion 42 is in a generally vertical rather than horizontal direction. In this case, the stationary contact 50 is mounted on a modified upright support bracket 52a having a horizontally extending upper portion 56, to which the contact 50 is secured in the path of movement of the movable contact 46. In the same manner as was previously described with reference to FIG. 1, the contact gap 54, being smaller in width than the gap 24 between the movable core part 20 and the leg 14 of the stationary core part 12, will limit angular pivotal movement of the free contact portion 42 of the armature about the fulcrum portion 38 thereof to a smaller angle than that of the horizontal leg 22 of the movable core part. Thus, when the coil 30 is energized, the resulting angular pivotal movements of the leg 22 and of the free flexible arm portion 44 will cause the latter to bow upwardly as shown in dashed lines in FIG. 2, effectively shortening its length and providing a transverse wiping or sliding movement of the movable contact 46 across the stationary contact 50 as indicated by the double arrow.

In FIG. 4, there is shown in detail the manner in which the free contact portion 42 of the armature member 34 flexes or bows between the open and closed positions of FIG. 1, it being evident that the arrangement of FIG. 2 is identical therewith except for the specific orientation of such free contact portion and the two contacts. FIG. 4 further illustrates the manner in which the inventive relay as described above may be readily adapted to provide a double-throw switching action through the addition of a respective further stationary and movable contact. In particular, the free contact portion 42 has secured thereto a second movable contact 56, preferably directly opposite the previously described movable contact 46, which co-operates with and normally engages a second stationary contact 58 mounted on a suitable upright support or bracket 60 generally similar to the bracket 52 and spaced therefrom, thereby defining a normally closed contact pair as shown in solid lines in this figure.

Preferably the bracket 60 and stationary contact 58 are so located relative to the free contact portion 42 of the armature 34 that the latter, due to its own spring resilience and particularly that of its fulcrum portion 40, biases the movable contact 56 into engagement with the stationary contact 58 with sufficient pressure to effect a reverse or inward bowing of the armature member, as shown in solid lines, when the coil 30 is nonenergized. Energization of the coil, as previously described, will effect pivotal movement of the free contact portion 42 and the contact 46 into engagement with the other stationary contact 50, effecting an outward bowing of the armature, as shown in dashed lines, and a corresponding sliding or wiping movement of the movable contact 46 upwardly across the stationary contact 50. However, it should also be noted that due to the initial inward bowing of the armature, the second movable contact 56 will exhibit a similar upward wiping or sliding movement across the second stationary contact 58 prior to disengagement or opening of these latter contacts. Reverse pivotal movement of the armature member 34, in a similar manner, will effect a downward wiping movement, in succession, of the two movable contacts across the respective stationary contacts.

As shown in FIG. 5, suitable electrical terminals are secured to the base and extend downwardly therefrom, for connecting the coil and the contacts 46 and 50 (as well as the additional contact 58 of FIG. 4, in the case of a double-throw relay) into appropriate circuitry. Thus, for example, a first depending terminal 62 is electrically connected to the stationary contact 50 through the conductive bracket 52, a second depending terminal 64 is connected to one lead 66 of the coil 30, and a third depending terminal 68 is connected jointly to the other lead (not shown) of the coil and to the anchorage portion 36 of the conductive spring armature 34, the latter in turn conducting current to the movable contact 46 secured to the end thereof. Thus it will be seen that the coil or actuating circuit extends across terminals 64 and 68, while the contact or relaycontrolled circuit is connected across terminals 62 and 68. In the double-throw embodiment of FIG. 4, it will of course be understood that an additional terminal,

not shown, would be electrically connected to the sec- 0nd stationary contact 58 in any suitable manner.

It will be appreciated that, due to the bowing of the free flexible arm portion 44 of the spring armature member 34, in turn effecting a wiping or sliding relative movement between the movable and stationary contacts in the manner described above with respect to each of the three embodiments, pitting and corrosion of the contacts resulting from arcing thereacross during each opening and closing cycle of the realy are substantially eliminated, thus making it possible for a relay of small physical size to carry very high DC currents, of the order of up to about 50 amperes. Further, since the armature member 34 pivots about a fulcrum defined solely by itself, or more particularly, by the spring fulcrum portion 40 thereof, and hence does not require an exterior or separate fulcrum-defining structure such as has been characteristic of prior known relay structures, shear forces are substantially eliminated and thus the inventive relay is characterised by a much longer service life and corresponding reliability than has heretofore been possible, providing well over 150,000 cycles without structural failure and possibly of an order approaching 1 million operating cycles.

It should further be evident that due to the configuration of the components of the inventive relay, and particularly of the magnetic core and the armature thereof, the relay may be rapidly assembled in a simple manner particularly suitable for use with automatic assembly apparatus. In particular, the mounting of the coil winding 30 and spool 32 upon one of the straight upstanding legs, shown as leg 14, of the generally U- shaped stationary core part 12 enables a significant part of the magnetic core and the armature to be preassembled prior to mounting of the coil 30. In particular, the stationary core part 12 may be formed into its illustrated shape, the coil 30 mounted on leg 14 thereof, and then the movable core part 20 and the armature 34, advantageously preformed as a single subassembly unit, may then be secured by the anchorage portion 36 of the armature to the other leg 18 of the stationary core part. In contrast, prior constructions utilizing a stationary magnetic core at least partially surrounding the coil have required that the coil be wound upon the unformed blank of the core and then the latter bent or otherwise formed into shape, thus requiring a considerably more difficult operation as well as raising the danger of mechanical damage to the comparatively delicate coil winding.

It should now be apparent from the above description that the inventive relay construction comprises in its basic form a stationary core part 12; a movable core part. 20'separated therefrom by a pair of core gaps 24 and 28 to define therewith a generally rectangular twopart magnetic core forming a closed magnetic flux circuit; a relay armature 34 formed of a single continuous strip of conductive spring material and defining an anchorage end portion 36 secured to the stationary core part 12, a curved spring fulcrum portion 40 adjacent to the anchorage end portion 36 and defining the sole fulcrum means for the armature, a support portion 38 adjacent the fulcrum portion and rigidly secured to the movable'core part 20, maintaining the latter spaced from the stationary core part 12 by the core gaps 24 and 28 and mounting the movable core part for pivotal movement about the stationary core part through a first angle 6,, a free contact portion 42 carrying movable contact 46, and a free flexible arm portion 44 connecting the contact portion 42 to the support portion 38 and being pivotally movable about the fulcrum portion through a second angle 0 smaller than 0,; and a coil 30 mounted on the stationary core part 12 for providing magnetic flux to the magnetic flux circuit when energized.

I claim as my invention:

1. A small DC relay for large currents and comprising: a stationary core part entirely defined by a single strip of ferrous material of uniform width and thickness; a movable core part formed of a further strip of said ferrous material and having a free end and adapted with said stationary core part to form a closed magnetic flux circuit therewith and when spaced therefrom to define first and second core gaps therebetween; a relay armature formed of a single strip of current conducting spring material of uniform section and having an anchorage end portion fixed to said stationary core part, a curved spring fulcrum portion forming the sole fulcrum of said relay armature and located next said anchorage portion, a support portion next said fulcrum portion and fastened rigidly to said movable core part and supporting the latter to defind a first pivotal angle of motion of the free end of said movable core part about said fulcrum, a free contact portion, and a free flexible arm portion between said contact portion and said support portion defining a second pivotal angle of motion of said flexible arm portion about said fulcrum less than the first pivotal angle; and a relay coil on said stationary core portion providing, when energized, magnetic flux for said magnetic flux circuit to effect pivotal movement of said movable core part and said flexible arm and said contact portions of said armature.

2. A small DC relay as claimed in claim 1, wherein said stationary core part is generall U-shaped in configuration and defines a pair of spaced, generally straight upstanding legs, said relay coil being mounted on and surrounding one of said upstanding legs, said anchorage end portion of said armature being defined between the upper end of said one of said upstanding legs and said free end of said movable core part, said second core gap being defined between the upper end of the other of said upstanding legs and an intermediate portion of said movable core part.

3. A small DC relay as claimed in claim 2, further comprising a'movable contact mounted on said contact portion of said armature and a stationary contact normally spaced therefrom by a distance less than said one of said core gaps, whereby closing of said contacts by energization of said relay coil will flow said flexible arm portion of said armature and effect a transverse wiping movement of said movable contact across said stationary contact,

4. A small DC relay as claimed in claim 1 wherein said armature is generally U-shaped, said free flexible arm portion and said free contact portion of said armature being bent generally perpendicular to said support portion thereof 5. A small DC relay as claimed in claim 1, wherein said free flexible arm portion and said free contact portion of said armature extend generally colinear to said support portion.

6. A small DC relay as claimed in claim 2, wherein said movable core is generally L-shaped andcomprises first and second generally perpendicular legs, said first leg extending generally horizontally and having a free end defining said free end of said movable core part, said second leg being secured to and depending from said first leg; and further comprising a further leg.se cured to the lower end of said second leg and extending generally parallel to said first leg and offset therefrom to define a generally Zshaped movable core member, said further leg being secured to said support portion of said armature, said intermediate portion of said movable core part comprising the juncture of said second leg and said further leg.

7. A small DC relay as claimed in claim 1, wherein said armature member consists of a ferrous material and effectively bridges one of said core gaps.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION 3,742,405 Dated June 26, 1973 Rodney Hayden et a1.

Patent No.

Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Under item [22] "August 2, 1970" should read August 2 1972 On the cover sheet insert I [30] Foreign Application Priority Data Canada 136,486 Mar. 6, 1972 Signed and sealed this 17th day of September 1974.

(SEAL) Attest:

C. MARSHALL DANN McCOY M. (mason JR. Attesting Officer Commissioner of Patents USCOMM-DC 60376-P69 1: us. GOVERNMENT PRINTING OFFICE: 1969 o--ase:ss4,

F ORM PO-IOSO (10-69) UNITED STATESPATENT OFFICE I CERTIFICATE OF CORBECTION 3 742 ,405 Dated June 26 1973 Rodney Hayden et a1.

Patent No.

Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Under item [22] August 2, 197Q" should read August 2 1972 w Ori the cover sheet insert I 130 Foreign ApplicationPriority Data Canada 136,486 I Mar. 6, 1972 Signed. and sealed this 17th day of September 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. c. MARSHALL DANN Commissioner of Patents Attesting Officer uscoMM-Dc ooan'pea 0.5. GOVERNMENT PRINTING OFFICE I958 O868:334,

F ORM Po-1oso (10-69) 

1. A small DC relay for large currents and comprising: a stationary core part entirely defined by a single strip of ferrous material of uniform width and thickness; a movable core part formed of a further strip of said ferrous material and having a free end and adapted with said stationary core part to form a closed magnetic flux circuit therewith and when spaced therefrom to define first and second core gaps therebetween; a relay armature formed of a single strip of current conducting spring material of uniform section and having an anchorage end portion fixed to said stationary core part, a curved spring fulcrum portion forming the sole fulcrum of said relay armature and located next said anchorage portion, a support portion next said fulcrum portion and fastened rigidly to said movable core part and supporting the latter to defind a first pivotal angle of motion of the free end of said movable core part about said fulcrum, a free contact portion, and a free flexible arm portion between said contact portion and said support portion defining a second pivotal angle of motion of said flexible arm portion about said fulcrum less than the first pivotal angle; and a relay coil on said stationary core portion providing, when energized, magnetic flux for said magnetic flux circuit to effect pivotal movement of said movable core part and said flexible arm and said contact portions of said armature.
 2. A small DC relay as claimed in claim 1, wherein said stationary core part is generall U-shaped in configuration and defines a pair of spaced, generally straight upstanding legs, said relay coil being mounted on and surrounding one of saiD upstanding legs, said anchorage end portion of said armature being defined between the upper end of said one of said upstanding legs and said free end of said movable core part, said second core gap being defined between the upper end of the other of said upstanding legs and an intermediate portion of said movable core part.
 3. A small DC relay as claimed in claim 2, further comprising a movable contact mounted on said contact portion of said armature and a stationary contact normally spaced therefrom by a distance less than said one of said core gaps, whereby closing of said contacts by energization of said relay coil will flow said flexible arm portion of said armature and effect a transverse wiping movement of said movable contact across said stationary contact.
 4. A small DC relay as claimed in claim 1 wherein said armature is generally U-shaped, said free flexible arm portion and said free contact portion of said armature being bent generally perpendicular to said support portion thereof.
 5. A small DC relay as claimed in claim 1, wherein said free flexible arm portion and said free contact portion of said armature extend generally colinear to said support portion.
 6. A small DC relay as claimed in claim 2, wherein said movable core is generally L-shaped and comprises first and second generally perpendicular legs, said first leg extending generally horizontally and having a free end defining said free end of said movable core part, said second leg being secured to and depending from said first leg; and further comprising a further leg secured to the lower end of said second leg and extending generally parallel to said first leg and offset therefrom to define a generally Z-shaped movable core member, said further leg being secured to said support portion of said armature, said intermediate portion of said movable core part comprising the juncture of said second leg and said further leg.
 7. A small DC relay as claimed in claim 1, wherein said armature member consists of a ferrous material and effectively bridges one of said core gaps. 